①. ____ for their support, he would have gone penniless.
A. Were it B. Were it not C. If it is not D. If it is
解析：本题考查虚拟语气哦省略+倒装用法。原句应该是：if it were not for their support..., 所以答案应该是B。句意是：如果没有他们的支持，他早就身无分文了。
②. I wish I ____ in the sun by a swimming pool instead of sitting in this classroom.
A.have lain B.were lying C.lay D.lie
解析：wish后面用虚拟语气，句意是：我多么地希望躺在泳池边享受阳光而不是坐在教室里。应该用与现在进行相对的时态，过去进行，所以答案是B。
③. The chairman insists that there ____ a meeting to be held within the shortest possible time.
A.is B.will be C.was D.be
解析：当insist表示“坚持认为”时，后面的宾语从句要用虚拟语气结构，should + do,当should被省略后，就留下动词原形，所以本题选择D。
④. He _____ the maths examination if he had worked hard enough, but he didn't。
A. would pass B. has passed
C. would have passed D. passed
解析：考查虚拟语气的用法。"假如他学习足够努力，他就通过数学考试了;但他(事实上)没有"。本句是对发生过的事情进行跟事实相反的假设。如果对发生过的事情假设，条件句中谓语部分用过去完成时态，结果主句中的谓语动词部分，应该配套用would(等情态动词)+ 现在完成时态。故选C。